Author Topic: rear spacers? different axle? help me out. (pics added) (Read 4539 times)

J.Webster Designs · « **on:** March 28, 2009, 02:38:58 PM »

hey guys, I am putting the rear end back together. I got it together and the nut is about 1/2 to 3/4 inch from going on to where i can get a cotter pin in. everything seems to be lined up properly as far as brakes, and chain. Does anyone have any information on spacer sizes???

The bike is a 1976 CB750F with 1976 CB750F rear rim. but it has a 1978 CB750F motor and 1978 CB750F cush drive.

i can get some detailed pictures if that will help you all out.

J.Webster Designs · « **Reply #1 on:** March 28, 2009, 05:32:15 PM »

Alan F. · « **Reply #2 on:** March 28, 2009, 05:34:48 PM »

Quote

1978 CB750F cush drive.

Sprocket carrier, or just rubber bits? I think the 77-78 sprocket carriers placed the sprocket a bit more to the left side of the bike than the earlier models.

Bump? dude, it's saturday night...

WFO · « **Reply #3 on:** March 28, 2009, 05:38:46 PM »

Do you have the spacers on the correct sides?

Quartza · « **Reply #4 on:** March 28, 2009, 05:39:34 PM »

Maybe your axle is the wrong year? Mine is 275mm between the head and threads.

J.Webster Designs · « **Reply #5 on:** March 28, 2009, 06:05:09 PM »

Quote

Sprocket carrier, or just rubber bits?

Sprocket carrier. It does shift the sprocket over about 10mm. I am trying to find out if I have the proper spacers or not. I am not sure what spacer sizes were offered. The axle that is in there now was used when the PO swapped to a comstar rim because he didnt know he could change out the sprocket carrier. It may be that the axle is small.. but it was tough getting that rear rim in there with the spacers that are on it now. I am thinking that the sprocket side spacer is not the right size. im thinking i need something about 10mm smaller. it may be a combination of both.

Quartza · « **Reply #6 on:** March 28, 2009, 06:25:50 PM »

On my 76 setup the sprocket side spacer sticks out about 7/16s. So if you run a late model engine you have to use a late model carrier?

J.Webster Designs · « **Reply #7 on:** March 28, 2009, 06:33:11 PM »

the 78 motor output sprocket is offset about 10mm so the 78 carrier is installed to match the offset.

Alan F. · « **Reply #8 on:** March 28, 2009, 06:39:55 PM »

Quote from: Quartza on March 28, 2009, 05:39:34 PM

Maybe your axle is the wrong year? Mine is 275mm between the head and threads.

That could be it, are you using your 76's axle?

J.Webster Designs · « **Reply #9 on:** March 28, 2009, 07:17:31 PM »

I am using whatever axle came in the bike... Like i said it was used with a comstar rim.... I will measure tomorrow and let you know what that measurement is. 275mm is a 76 axle?

754 · « **Reply #10 on:** March 28, 2009, 07:31:15 PM »

The cush drive is longer, so you need a SHORTER or SHORTENED spacer between it and the swing arm.. because you have the earlier arm..
Or get the longer axle but you probably got to shim under the nut then.

J.Webster Designs · « **Reply #11 on:** March 28, 2009, 08:07:41 PM »

is there some place that i can look at the axle lengths or the spacer sizes? would it be safe to take down a spacer a couple mm?

Steve F · « **Reply #12 on:** March 28, 2009, 08:20:52 PM »

The axle is too short. Axle spacers should have no effect on nut position on the axle. Just slide only the axle with the chain adjusters into the swingarm slots where the axle goes without the wheel, and you should be able to bottom the nut (finger tight) and still get to the cotter pin hole. Remember, the swingarm width is set, and you don't squeeze anything when putting it all together. The spacers allow for proper alignment of the wheel, sprocket and on the "F" model the brake rotor/caliper too. When properly assembled with all the proper parts, the whole assembly including the chain adjusters and the caliper should slide nice and snug between the swingarm sides. No excess play or gaps, and also shouldn't have to be forced either. It's all designed so that things go together without adding stresses to the swingarm or having to improvise.
Steve F

J.Webster Designs · « **Reply #13 on:** March 28, 2009, 08:29:04 PM »

thats the thing though... I had to "stretch" the swingarm OPEN about a mil or so to slide in the last chain adjuster in. so im trying to figure out if any of the other spacers will fix this problem or if i ONLY have axle problems... I appreciate all the help guys... I will get some pics posted tomorrow showing what is going on. the sprocket side of the swingarm is also VERY close to the rear peg bolt. I think that it will hit if i take a right hand turn and it flexes the swingarm in that direction.

754 · « **Reply #14 on:** March 28, 2009, 08:57:32 PM »

Its just the left side spacer, you may have the 78 one in the carrier, or they are the same and the inside one is longer.
Either way unless you have a shorter one, it is safe to cut it down. Now without a lathe it gets a bit tricky, but with a square, and being careful you can get it good enough. (calipers to measure length in a few spots would help)

Industrial Cafe · « **Reply #15 on:** March 28, 2009, 09:36:36 PM »

should be an easy fix when you see what you gotta do.
I had to make my own spacers by cutting down a big one to center the wheel in the dohc swing arm on my sohc k1 bike with a K8 motor. *gasp*

I agree with Steve F, there should be no stress on the swing arm when putting the assembly together.

J.Webster Designs · « **Reply #16 on:** March 29, 2009, 12:52:40 PM »

i pulled the rear axle out and between the head of the axle bolt and its threads is right around 11 inches. thats 279.4mm. It needs to be right around 10 mm longer or the spacer needs to be 10mm smaller. anyone know what the size of the 76 or 78 sprocket side spacers are? or if there is an axle that is 10mm longer than the one that i have?

J.Webster Designs · « **Reply #17 on:** March 29, 2009, 01:05:32 PM »

I am thinking that the sprocket side spacer is the problem.

Steve F · « **Reply #18 on:** March 29, 2009, 02:45:20 PM »

Let's just FORGET the alxe at this point, OK? Take everything that is supposed to fit between the swingarm mounts, and assemble everything in the proper sequence, including the chain adjusters. Does everything fit or not? If too wide, you have the wrong parts. If too narrow, you have the wrong parts. If the axle appears to not have enough threads, you have the wrong axle. Don't go about modifying stuff to get things to "fit".

Industrial Cafe · « **Reply #19 on:** March 29, 2009, 03:10:37 PM »

For Gods sake, post pictures of what you got!

we need to see whats really goin on.
some of us can recognize spacers and problems just by looking at them.

hmm.. try this
center the wheel so the chain is lined up without the spacers installed, then measure the spaces, and cut or make up spacers accordingly.

are you still using the 630 chain for the 78 motor?

J.Webster Designs · « **Reply #20 on:** March 29, 2009, 04:14:19 PM »

camera is charging........ will post pics soon

Industrial Cafe · « **Reply #21 on:** March 29, 2009, 04:38:39 PM »

J.Webster Designs · « **Reply #22 on:** March 29, 2009, 06:38:11 PM »

ok guys... here we go....

located properly....

brake rotor lined up properly...

brake side spacer....

Industrial Cafe · « **Reply #23 on:** March 29, 2009, 06:45:56 PM »

alright, just measure up your gap on the chain side and grind down the spacer to fit exactly in that gap.
problem solved?

J.Webster Designs · « **Reply #24 on:** March 29, 2009, 06:47:02 PM »

amount of threads showing with everything installed....

with washer added....

nut installed and torqued down....

the rear peg bolt clearance to swing arm on sprocket side....

tried to show chain alignment.... it looks pretty dang straight....

remember... I had to stretch open the sprocket side of the swing arm slightly (maybe a 1/16 or so) to get the sprocket side chain adjuster installed. That clearance on that nut for the center stand stop has me worried and is kinda telling me that the sprocket side spacer is off by 10mm. If i turn down the sprocket side spacer then it will allow for easier installation of the entire assembly and will make the clearance of that nut MUCH more acceptable....

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Author Topic: rear spacers? different axle? help me out. (pics added) (Read 4539 times)

Quartza

Quartza